Change eliminateCallFramePseudoInstr() to return an iterator

This will become necessary in a subsequent change to make this method
merge adjacent stack adjustments, i.e. it might erase the previous
and/or next instruction.

It also greatly simplifies the calls to this function from Prolog-
EpilogInserter. Previously, that had a bunch of logic to resume iteration
after the call; now it just continues with the returned iterator.

Note that this changes the behaviour of PEI a little. Previously,
it attempted to re-visit the new instruction created by
eliminateCallFramePseudoInstr(). That code was added in r36625,
but I can't see any reason for it: the new instructions will obviously
not be pseudo instructions, they will not have FrameIndex operands,
and we have already accounted for the stack adjustment.

Differential Revision: http://reviews.llvm.org/D18627

llvm-svn: 265036

4 files changed, 8 insertions, 9 deletions

diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index fec2224a65b..488dfb48dbf 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -1726,10 +1726,9 @@ void ARMFrameLowering::determineCalleeSaves(MachineFunction &MF,
   }
 }
 
-
-void ARMFrameLowering::
-eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
-                              MachineBasicBlock::iterator I) const {
+MachineBasicBlock::iterator ARMFrameLowering::eliminateCallFramePseudoInstr(
+    MachineFunction &MF, MachineBasicBlock &MBB,
+    MachineBasicBlock::iterator I) const {
   const ARMBaseInstrInfo &TII =
       *static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
   if (!hasReservedCallFrame(MF)) {
@@ -1769,7 +1768,7 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
       }
     }
   }
-  MBB.erase(I);
+  return MBB.erase(I);
 }
 
 /// Get the minimum constant for ARM that is greater than or equal to the
diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.h b/llvm/lib/Target/ARM/ARMFrameLowering.h
index 66f4dfb6ef5..21cd78da395 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.h
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.h
@@ -74,7 +74,7 @@ public:
                    bool(*Func)(unsigned, bool),
                    unsigned NumAlignedDPRCS2Regs) const;
 
-  void
+  MachineBasicBlock::iterator
   eliminateCallFramePseudoInstr(MachineFunction &MF,
                                 MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator MI) const override;
diff --git a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
index 09f7a493241..ef225f34abb 100644
--- a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
+++ b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
@@ -49,7 +49,7 @@ emitSPUpdate(MachineBasicBlock &MBB,
 }
 
 
-void Thumb1FrameLowering::
+MachineBasicBlock::iterator Thumb1FrameLowering::
 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I) const {
   const Thumb1InstrInfo &TII =
@@ -80,7 +80,7 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
       }
     }
   }
-  MBB.erase(I);
+  return MBB.erase(I);
 }
 
 void Thumb1FrameLowering::emitPrologue(MachineFunction &MF,
diff --git a/llvm/lib/Target/ARM/Thumb1FrameLowering.h b/llvm/lib/Target/ARM/Thumb1FrameLowering.h
index 27faac63683..9de1ba1d700 100644
--- a/llvm/lib/Target/ARM/Thumb1FrameLowering.h
+++ b/llvm/lib/Target/ARM/Thumb1FrameLowering.h
@@ -41,7 +41,7 @@ public:
 
   bool hasReservedCallFrame(const MachineFunction &MF) const override;
 
-  void
+  MachineBasicBlock::iterator
   eliminateCallFramePseudoInstr(MachineFunction &MF,
                                 MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator MI) const override;